Steam reforming of 1-methylnaphthalene over olivine and olivine supported nickel

Transcription

1 Steam reforming of 1-methylnaphthalene over olivine and olivine supported nickel Rudy Michel 1, René Gruber 1 *, Agata Łamacz 2, Andrzej Krzton 2, Claire Courson 3, Gérald Djéga-Mariadassou 2, Philippe Burg 1 1 Laboratoire de Chimie et de Méthodologies pour l'environnement (LCME) Université Paul Verlaine - Metz, UFR SciFA 1, Bd Arago, technopôle 2, 5778 Metz cedex 3, France; gruber@univ-metz.fr 2 Centre of Polymer and Carbon Materials, Polish Academy of Sciences, Marii Curie-Sklodowskiej 34, Zabrze, Poland 3 Laboratoire des Matériaux, Surfaces et Procédés pour la Catalyse (LMSPC) Université Louis Pasteur, 25 rue Becquerel 6787 Strasbourg Cedex 2, France Introduction The catalytic steam gasification of Miscanthus X Giganteus in fluidized bed has shown the production of high-grade synthesis gas. This product gas can be used for a wide range of applications like synthesis (biofuels, methanol, chemicals) or electricity production (hydrogen fuel cell, gas turbine or engine). The aim is to obtain hot gas clean-up, however one of the main problems of biomass gasification processes is the presence of tars in the product gas. As a result steam reforming processes seems to be the best way for tar elimination [1, 2]. Olivine, a magmatic rock, is often studied in geology. According to Portnyagin et al, the inclusions in olivine can rapidly and selectively exchange water, probably with the matrix melt, through combination of proton diffusion and molecular water transport along dislocations inside the olivine [3]. Olivine, has already demonstrated activity in tars conversion [1,4,5,6]. It presents high attrition resistance, is cheap and can be used as a primary catalyst directly in fluidized bed gasifiers [7]. However tar removing with olivine is not enough satisfactory for the applications of the product syngas. Indeed, Ni based catalysts are the most often studied [1, 4, 6, 8] for their high tars destruction activity in steam reforming. We have reported (GDRI 29) that naphthalene is the major tar compound in high temperature issue of catalytic steam gasification of Miscanthus X Giganteus. Thus it is indicate as model for steam reforming. However, physical properties of naphthalene are not adequate for our reforming process. In this way, 1-methylnaphthalene is used. Catalytic steam reforming of 1-methylnaphthalene is carried out in a fixed bed reactor. The results of conversion, the percentage of H 2, CO, CO 2 and water effect are presented. Catalysts are analysed by XRD and SEM. Experimental part The experimental system of reforming is shown in Figure 1. All the experiments were carry out in the Centre of Polymer and Carbon Materials, Polish Academy of Sciences (Gliwice, dr A.Krzton)

2 Catalysis for Environment: Depollution, Renewable Energy and Clean Fuels Zakopane, MS 9 PQ Mass flowmeters 9. Gas Chromatograph 2. Hydrocarbons saturator 1. FID detector 3. Water saturator 11. Feeding loop 4. Thermostat 12. Switching loop 5. Cryostat 13. Computer with integrator 6. Gas mixer 7. Oven with temperature regulator 8. Quartz reactor He or Ar Fig.1. dispositive of reforming installation The reforming is performed in a quartz U-type reactor in the presence of 59 ppm of 1-methylnaphthalene (MNP) and 1ppm of steam in argon as a balance [9]. The flow rate is fixed at 25ml/min, three different quantities of catalyst are tested to change the time contact. During the isotherms carry out in temperatures ranging from 9 to 6 C, the composition of evolved gas (H 2, CO and CO 2 ) is measured by gas chromatography. The contact time of gas with the catalyst is defined according the following equation: = mcat (m cat and ρ are respectively the masse and the density of the catalyst and Q t ct ρ. Q is the gas flow). Results and discussion Steam reforming in isotherm conditions The reaction pathway is described by reactions (1) and (2). C 11 H H 2 O 11CO + 16H 2 (1) CO + H 2 O CO 2 + H 2 (2) According to the reaction (1), the theoritical value of H 2 /CO (1.45) depends also of the importance of the WGS reaction (2), which consume CO and produce H

3 Zakopane, 29 Catalysis for Environment: Depollution, Renewable Energy and Clean Fuels 16 H a Conversion in CO+CO 2 2 CO CO Temperature ( C) 5 4 2b H 2 3 Conversion in CO+CO CO CO Temperature ( C) Fig. 2. Conversion of MNP with olivine (2a)and Ni-olivine (2b) The Figure 2 shows the results of isotherms reforming of MNP with olivine and Ni-olivine. Percentages of gases are given according to the limited reagent (MNP) at T ct =.17s. In the presence of olivine (2a), a low conversion of MNP with weak hydrogen content is observed for all experiments. The most interesting results are obtained at 9 C: In the case of olivine alone, the high H 2 /CO ratio (8.7) suggests a consumption of CO by water gas shift reaction, with production of H 2. The use of Ni-olivine catalyst improves the conversion rate up to 33 with a H 2 /CO ratio of 3.3, but the conversion remains insufficient. In fact, the reaction leads to coke formation on the catalyst s surface and bring about its deactivation. Effect of water pre-treatment on the catalyst According to Baláž and all [1], a pre-treatment with water, before reforming, would allow getting better the results of conversion and gases content. The Figure 3 presents the obtained yields of H 2 and CO with (AT) and without (BT) pre-treatment with water 2 minutes before reforming at 9 C. T ct =.17s H 2 -AT H 2 -BT CO - AT CO - BT Time (min) Fig. 3. Effect of water treatment on H 2 and CO content 129

4 Catalysis for Environment: Depollution, Renewable Energy and Clean Fuels Zakopane, 29 After water pre-treatment of the catalyst, the production of H 2 and CO is doubled without changing for CO 2. The production of H 2 and CO is due to the water decomposition (3) and carbon consumption (4). H 2 O H 2 + O (3) C + O CO (4) Steam reforming before isotherm To estimate the Ni-olivine catalyst s efficiency, we measure the gases composition, versus the time, before the carbon formation with pre-treatment of water. The Figure 4 shows the results of MNP reforming with Ni-olivine. T ct =.17s. 9 H 8 2 Conversion CO 1 CO Temperature ( C) Fig. 4. Reforming of MNP After 17 minutes, the conversion reaches 75 (instead of 33) with high H 2 content at 9 C. Ni-olivine shows the best result, before the overall carbon coating and the pretreatment. The ratio H 2 /CO is about 3.4 instead of 1.45, due to the carbon formation. Analysis of the catalyst after reforming The Figure 6 shows the diffractograms of Ni-olivine and Ni-olivine after reforming. 4 Ni-olivine Ni-olivine ref NiO Ni 3 Lin (Cps) Θ Fig. 6. Diffractograms of Ni-olivine 13

5 Zakopane, 29 Catalysis for Environment: Depollution, Renewable Energy and Clean Fuels During the reforming, the peaks of NiO disappear (2Θ=37.2, 44.6 and 62.7 ). We observed the presence of the peaks which can be assigned to the Ni metal (2Θ=44.5 and 54 ). Like this, the reduction of NiO in Ni metal is confirmed by SEM in Figure 7. Fig. 7. SEM of Ni-olivine after reforming Counts Si Mg Fe Distance (µm) Ni Conclusion The main findings of the MNP reforming experiments can be underlined as following: Whatever the conditions, NiO have a positive effect of MNP conversion in H 2 and CO, more especially at high temperature (9 C) Nevertheless, a pre-treatment of the catalyst by water improved the conversion. This effect may be due to the higher specific area (BET) produced by water [3]. In other respects, concerning the behaviour of the Ni olivine catalyst, we have observed the formation of Ni metal during the process At last, a coating by carbon formation deactivates the catalyst which can be reduced by use of more water. References [1] D. Swierczynski, C. Courson, A. Kiennemann, Chemical Engineering and Processing (27). [2] T.A. Milne and R.J. Evans, November (1998) NREL/TP [3] Maxim Portnyagin, Renat Almeev, Sergei Matveev, François Holtz, Earth and Planetary Science Letters, 272 (28) 541. [4] C. Courson, L. Udron, D. Swierczynski, C. Petit, A. Kiennemann, Catalysis Today, 76 (22) 75. [5] L. Devi, K.J. Ptasinski, F.J.J.G. Janssen, S.V.B. van Paasen, P.C.A. Bergman, J.H.A. Kiel, Renewable Energy, 3 (25) 565. [6] D. Swierczynski, S. Libs, C. Courson, A. Kiennemann, Applied Catalysis B: Environmental, 74 (27) 211. [7] S. Rapagnà, N. Jand, A. Kiennemann, P.U. Foscolo, Biomass and Bioenergy, 19 (2) 187. [8] T. Wang, J. Chang, X. Cui, Q. Zhang, Y. Fu, Fuel Processing Technology, 87 (26) 421. [9] A. Łamacz, A.Krztoń, A. Musi, P. Da Costa, G. Djéga-Mariadassou, International Groupe of research (GDRI), Procedings Zakopane 28. [1] P. Baláž, E. Turianicová, M. Fabián, R.A. Kleiv, J. Briančin, A. Obut, Int. J. Miner. Process., 88 (28)

6 Catalysis for Environment: Depollution, Renewable Energy and Clean Fuels Zakopane,